7921 ‎(2)‎

• UCREFRP Catalog Number: 7921
• Author: Trembly, T. L. and G. A. Gould.
• Title: Opportunities To Protect Instream Flows In Colorado And Wyoming.
• USFW Year: 1987.
• USFW - Doc Type: Biological Report 87‎(10)‎,
• Copyright Material: NO

Information about the relationships between striped bass habitat suit-
ability and a few variables is substantial, but information for many variables
is sparse. Available data indicate that dissolved oxygen concentration, water
temperature, and velocity are the principal variables that limit riverine
habitat suitability for striped bass; dissolved oxygen concentration and water
temperature are the principal variables that limit lacustrine habitat
suitability.
Food. Food availability may not directly limit the suitability of repro-
ductive habitat because adults do not feed immediately before and during
spawning (Woodhull 1947; Morgan and Gerlach 1950; Hollis 1952; Stevens 1966;
Trent and Hassler 1966; Manooch 1973). However, their feeding habits during
spawning runs are unclear. Larvae do not feed until they are 5 to 8 days of
age (Doroshev 1970; Humphries and Cumming 1973) and may not begin to feed
until they reach lacustrine or estuarine habitat.
Availability of prey (zooplankton) during the first few days of feeding
is likely a critical factor influencing the survival of striped bass larvae
(Miller 1977; Cooper and Polgar 1981; Eldridge et al. 1981). Miller (1977)
reported that a minimum of 1,864 zooplankters per liter is required by larvae
during initial feeding; however, striped bass larvae begin feeding and
apparently survive in some waters in California, where average concentrations
of zooplankton are much lower (Crance 1985). A zooplankton density of 4,000/1
or more was reported to be optimal for young juveniles.
Landlocked adults feed primarily on gizzard shad and/or threadfin shad
(Stevens 1958; Mensinger 1971; Ware 1971; Edwards 1974; Bailey 1975; Weaver.
1975; Combs 1978; Deppert and Mense 1979; Gustaveson et al. 1980; Persons and
Bulkley 1982). The quantity of forage fish required likely depends on several
interacting variables, including the size of the striped bass population to be
sustained and the presence of other species that eat shad or that are eaten by
striped bass. An established population of striped bass has been maintained
in Arkansas waters where the clupeid standing crop average was as low as
22.4 kg/ha (20 lbs/acre), but a standing crop of about 84.1 kg/ha (75 lbs/acre)
or higher is probably optimal (Crance 1985).
Water flow. Diversions of instream flow may block spawning migrations or
alter water depth, width, velocity, and/or other variables to levels critical
for spawning and survival of eggs and larvae. Stable, high volume stream flow
and water velocity during the spawning season probably enhance suitability of
reproductive habitat by helping to stabilize the water temperature, facilitate
the migration of spawning adults, suspend eggs until hatching, and buoy larvae
until suspension can be maintained by swimming. Streams suitable for repro-
ductive habitat generally are characterized as having large volumes of moving
water (Pearson 1938; Raney 1954; Fish and McCoy 1959; Mansueti and Hollis
1963; Turner and Chadwick 1972) and uniform flows (Fish and McCoy 1959). High
volume stream flow may result in the emigration of striped bass -from the
receiving reservoir if the reservoir has a short retention time.
Simultaneously rising discharges and water temperatures may have resulted
in striped bass migrating upstream to spawning sites in the John H. Kerr
Reservoir system, while very erratic stream flows, with or without rising
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